The present invention relates to a semiconductor memory device. For example, the present invention relates to a technology for eliminating a leak current generated when data is written into a memory cell.
A circuit for performing a write by causing a constant current to flow between the source and drain of a memory cell is disclosed in Japanese Unexamined Patent Application Publication No. 2005-276347. The circuit causes a current source circuit to pass a preset constant current along a path from a selected source line to a selected cell source, a selected cell drain, and a selected bit line by applying a source voltage to the selected source line and applying a gate voltage to a selected word line. In this instance, channel hot electrons, which are generated by the constant current flowing into a selected memory cell, are injected into a floating gate to write data in the selected memory cell.
Meanwhile, a semiconductor memory adapted to eliminate a leak current delivered by an unselected memory cell is disclosed in Japanese Unexamined Patent Application Publication No. 2011-170941. The semiconductor memory locates a source line coupled to a memory cell row including a memory cell into which data is to be programmed, and sets the located source line to a high-level voltage. Further, the semiconductor memory locates a source line coupled to a memory cell row into which data is not to be programmed, and sets the located source line to a voltage that is higher than a low-level voltage of a selected gate line and lower than a high-level voltage of an unselected bit line.